It is already known that certain substituted benzoylcyclohexanediones have herbicidal properties (cf. EP-A-090262, EP-A-135191, EP-A-186118, EP-A-186119. EP-A-186120, EP-A-319075, WO-A-96/26200, WO-A-97/46530, WO-A-99/07688). However, the activity of these compounds is not in all respects satisfactory.